Thrust reversers, such as pivot door-type and cascade-type reversers, are utilized on many different aircraft. The typical pivot door-type reverser includes a fixed structural component, rotating pivot doors, and an actuation system. When commanded to deploy, actuators force the doors to rotate to a predetermined angle, blocking the rearward airflow and turning it forward at an angle approximately equal to the rotated door angle. The pivot door position and angle turn the airflow forward to provide reverse thrust to improve deceleration early in the landing roll when residual aerodynamic lift and high speed limit the effectiveness of mechanical braking. The doors extend well into the external airstream when deployed and include so-called kicker plates, side fences, and/or other flow control devices to help direct the flow forward.
The typical translating sleeve cascade-type reverser includes a fixed structure component, a sliding external sleeve, pivoting blocker doors, a cascade structure, and an actuation system. When commanded to deploy, actuators translate the external sleeve aft and expose an area common to the cascade structures. The blocker doors deploy as the sleeve translates to block the exhaust flow and redirect it through the cascade. The cascade includes vanes specifically designed to both efficiently turn the airflow forward and control the efflux.
Additionally, a pivot door-type reverser having a cascade arrangement is known in which the cascade is stationary and requires the outer portion of the nozzle to translate while inner doors pivot to block the airflow.
Area match, reverse thrust effectiveness, and air efflux pattern are key aerodynamic performance measures that govern much of the design of thrust reversers. Area match is a ratio of the air mass flow during reverse thrust to the air mass flow during forward thrust (when the reverser is stowed). To ensure safe operation the air mass flow in reverse mode should nearly match or exceed the mass flow in forward mode; consequently, the reverse mass flow requirement is usually around 105% to 110% of the forward mass flow.
The reverse thrust effectiveness is a ratio of the actual reverse thrust versus the theoretically available reverse thrust, and determines how well the reverser will assist in braking of the aircraft during landing or refused take-off. Because the thrust reverser is considered a supplement to the wheel brakes, the reverse thrust effectiveness requirement is at the aircraft manufacturer's discretion, but aircraft operators want to maximize this capability. Recently, a demand for higher efficiency pivot door reversers has been evident in the industry.
Efflux control ensures the reverse airflow does not overly impinge on the surrounding aircraft structure or result in ingestion of air or debris into the engine. The efflux pattern is unique to each application, but in general requires the reverser to include aerodynamic flow devices to properly direct the reverse airflow.
Pivot door-type reversers have achieved effectiveness values in the range of 20% to 30%. In theory, higher effectiveness could be achieved by changing the door position and geometry to provide a higher forward thrust force. However, the necessary geometry changes result in the door length increasing to preserve aerodynamic equivalency, and the door must be adjusted rearward in order to maintain the required flow area for safe engine operation. A larger door placed further aft on the fixed structure challenges the typical turbofan nozzle envelope and can result in compromises to the external flow surface and nozzle exit surface. On the other hand, cascade-type reversers, readily achieve effectiveness values near 40% without compromising the external or internal flow surfaces. However, some weight penalties are usually incurred over pivot door-type reversers with the addition of the translating structure and the extra weight of the cascade baskets.
This background discussion is intended to provide information related to the present invention which is not necessarily prior art.